Engines, in particular diesel engines, can enter an uncontrolled state known as ‘run away’. In this state the engine experiences unrestrained combustion and if not stopped, the engine can reach destructive speeds that can result in catastrophic engine failure, and even personal injury to those in proximity. There are a number of causes of run away in engines including, without limitation, a faulty engine governor, engine overheating or the ingestion of unregulated hydrocarbons into the combustion chamber. Such hydrocarbons may be from an external source such as gaseous airborne forms, or from the engine itself due to a malfunction such as failure of turbo charger oil seals.
The conventional way to stop a diesel engine is to stop the flow of fuel to the combustion chamber. However, an alternate method must be employed to stop a diesel engine in the event of run away. The most common method used involves removing the air supply to the combustion chamber. Once deprived of oxygen, the uncontrolled combustion ceases. Accordingly, safety valves which cut off the air supply to the engine have been developed to shut off the engine in such a situation.
Typical shut-off valves are positioned in the air intake to the engine and employ a valve that is spring biased to be in a closed position that blocks air supply to the combustion chamber. The spring loaded valve is held in an open position by a solenoid or by other appropriate restraint means, thereby allowing an unobstructed air supply into the engine. Upon run away occurring, there is a de-activation of the restraint means, and the valve snaps into its closed position, thus cutting off the air supply to combustion chamber and starving the engine of air until it stalls. Other variations of cut-off valve systems employing various activation means have also been developed, but all commonly employ a system whereby a valve snaps shut upon receipt of some form of stimulus. The instantaneous removal of the air supply using such a conventional valve systems results in significant amount of un-burnt diesel fuel remaining in the engine. The pooled fuel can have a deleterious effect on engine components. Further, upon subsequent start-up of engine after shut down, the fuel loaded engine can experience smoking, engine noise, and even engine damage.
It is, therefore, desirable to provide a shut-off valve which mitigates these limitations.